Experimental evidence that evolutionarily diverse assemblages result in higher productivity

Abstract

There now is ample experimental evidence that speciose assemblages are more productive and provide a greater amount of ecosystem services than depauperate ones. However, these experiments often conclude that there is a higher probability of including complementary species combinations in assemblages with more species and lack a priori prediction about which species combinations maximize function. Here, I report the results of an experiment manipulating the evolutionary relatedness of constituent plant species across a richness gradient. I show that assemblages with distantly related species contributed most to the higher biomass production in multispecies assemblages, through species complementarity. Species produced more biomass than predicted from their monocultures when they were in plots with distantly related species and produced the amount of biomass predicted from monoculture when sown with close relatives. This finding suggests that in the absence of any other information, combining distantly related species in restored or managed landscapes may serve to maximize biomass production and carbon sequestration, thus merging calls to conserve evolutionary history and maximize ecosystem function.

Keywords: biodiversity; phylogenetic diversity; transgressive overyielding.

Fig. 1.

(A) The time-calibrated molecular ML phylogeny of the species used in this experiment. The gray arrowheads indicate example two-species combinations that constitute the phylogenetic treatments. (B) PD across realized richness. Treatments produced a gradient in PD within each richness level.

Fig. 2.

The relationship between plot biomass production and species richness (A) and PD (B). Lines are estimated from linear regressions, with models shown in the upper left of each plot.

Fig. 3.

The complementarity effect was significantly related to several diversity measures, including richness (A) but was explained best by PD (B; ●, plots exhibiting transgressive overyielding). The selection effect was predicted best by a phylogenetic measure that quantified the imbalance of abundances across the nodes in the phylogeny (IAC) (C). The single best predictor of the overall biodiversity effect was PD (D).